The invention relates to a moisture meter, particularly for masonry materials such as concrete or gypsum structures.
Concrete floors must be allowed to dry to an adequate level before they are covered with sheet, tiles, coatings or timber flooring. Excess moisture could lead to problems of condensation causing swelling and peeling of the covering and condensation, blistering or deterioration of adhesives leading to flooring failure.
No period can be specified for the drying of concrete as this is affected by temperature and humidity within the building. For this reason the concrete slab should be regularly checked to monitor the drying process.
Japanese Patent Specification No. JP11006797 describes measurement of moisture content of cast concrete. The system uses infra-red radiation at a multiplicity of locations in a grid.
The invention is directed towards providing a moisture meter which allows simpler determination of masonry moisture content with excellent accuracy.
According to the invention, there is provided a moisture meter comprising:
a hand-held housing;
a controller;
an input interface;
an output interface;
an electrical impedance sensor connected to the controller;
a relative humidity probe connected to the controller;
means in the controller for processing signals from the impedance sensor to generate a moisture content output, and for processing signals from the relative humidity probe to generate a relative humidity output.
In one embodiment, the controller comprises means for storing material parameter datasets for each of a plurality of materials, means for allowing user selection of a relevant dataset, and means for processing input signals according to the selected dataset.
In another embodiment, the controller comprises means for storing a dataset for each of concrete and gypsum.
In a further embodiment, the controller comprises means for storing a dataset for each of a plurality of concrete and gypsum types.
In a further embodiment, the relative humidity probe further comprises a temperature sensor and the controller comprises means for processing input signals from said sensor and for generating a temperature output.
In one embodiment, the impedance sensor comprises capacitive electrodes and associated drive and pick-up circuits.
Preferably, each electrode comprises a plurality of spring-loaded contacts for uniform contact with material.
In one embodiment, the drive frequency is approximately 125 kHz.
In another embodiment, the controller comprises means for storing a data record for each measurement of the impedance sensor and of the relative humidity probe.
In a further embodiment, the relative humidity probe further comprises a temperature sensor and the controller comprises means for writing temperature data to a relative humidity data record.
In one embodiment, the relative humidity probe comprises a capacitive sensor, a pulse width modulator for modulating output of the capacitive sensor and an averaging filter for averaging the modulated signal.
In one embodiment, the probe further comprises a digital microcontroller connected to receive an output from the averaging filter via an analog to digital converter.
In a further embodiment, the probe comprises a housing of tubular shape comprising openings at an inner end for access by air to internal sensing components.
Preferably, the probe housing is of castellated shape at its inner end.
In one embodiment, the probe further comprises a grommet comprising means for sealing around the probe at the mouth of a bore.
In another embodiment, the probe further comprises a sleeve comprising means for receiving the probe body when inserted in a bore.
In one embodiment, the sleeve is a friction fit within the grommet as describe above.
According to another aspect, the invention provides a moisture meter comprising:
a hand-held housing;
a controller;
an input interface;
an output interface;
a relative humidity probe connected to the controller;
means in the controller for processing signals from the relative humidity probe to generate a relative humidity output; and wherein
said relative humidity probe comprises:
a tubular housing containing sensing components, said housing having openings at an inner end thereof,
a sleeve comprising means for receiving the probe housing and having openings at an inner end thereof,
a grommet within which the sleeve is a friction fit, said grommet comprising means for engaging the rim of a bore to seal an annular gap around the sleeve when inserted in a bore, and
a plug comprising means for sealing an outer opening of said sleeve to create a confined sensing space within the sleeve before insertion of the probe housing.